Conventional erbium doped fiber amplifiers (EDFA) have been extensively used in optical telecommunications as means to amplify weak optical signals in the third telecommunication window (near 1550 nm) between telecommunication links. Much work has been done on the design of these amplifiers to provide efficient performance, such as high optical gain and low noise figure. However, with the recent enormous growth of data traffic in telecommunications, owing to the Internet, intranets, and e-commerce, new optical transmission bandwidths are required to provide increased transmission capacity in dense wavelength division multiplexing (DWDM) systems.
There are a few solutions to this demand. One proposed solution is to utilize new materials compositions as a host for the fiber gain medium (instead of silica), such as telluride, which may provide broader amplification bandwidth (up to 80 nm). However, the non-uniform gain shape and poor mechanical properties of telluride glass make these amplifiers difficult to implement in telecommunication systems. Also, Raman amplifiers can be considered as an alternative solution to high bandwidth demand, since these amplifiers are capable of providing flexible amplification wavelength with a broad bandwidth. However, these amplifiers place restrictions on optical system architectures because of their required designs for efficient performance, such as long fiber length (>5 km), high pump power (>500 mW) and co-pumping configurations. On the other hand, relatively long erbium doped fibers (EDFs) may also provide amplification in the long wavelength range (1565-1620 nm) when they are used with high power pump sources. This range is commonly called “L band”, which can be further subdivided in a 1565-1605 nm range and a 1605 nm and greater range, which is referred to as “ultra-L band”. The conventional range, currently being used for most commercial applications, also known as “C band”, is in the wavelength range between 1520-1565 nm.
With the need to increase transmission capacity to accommodate the rapid growth of optical telecommunications, the industry is looking to L band and possibly ultra-L band as solutions to this need. However, in order to amplify C band, L band, and ultra-L band signals, multiple amplifiers are currently required. It would be beneficial to provide a single optical amplifier that amplifies a light signal over a large bandwidth encompassing C band, L band, and ultra-L band light.